Printing a document is usually one of the easiest things you can do on a Mac. Select File -> Print, and you're pretty much done. That is, unless your printer refuses to print. Restocking the printer's paper tray will often solve the problem, but when obvious solutions like that don't work, figuring out what to do can be a difficult and time-consuming troubleshooting task. If your printer completely stops printing, the best thing to do is to start with the basics:
1. Check the power
Make sure your printer is turned on and has power.
2. Check the paper
Make sure you have paper in the paper tray. Typically, if there's no paper, you'll see an alert on either your Mac's display or the printer's LCD panel. Check the printer even if no error message pops up on your screen.
3. Check the connection
Check that the cable (probably USB) connecting the printer to your Mac or router is plugged into its appropriate port. If necessary, try a different USB port.
4. Check what's selected
If you have more than one printer connected to your Mac, make sure that you've selected the one you want, in the Print dialog box's Printer pop-up menu. For example, if you've selected a printer that's currently turned off, nothing will happen.
Tip: If subsequent visits to the Print dialog box reveal that the Printer pop-up menu has reverted back to the wrong printer, go to the Print & Fax system preference. From the Default Printer pop-up menu, select your desired printer.
(Image Caption: If the wrong printer keeps showing up in the Print dialog box, make sure you've designated the printer you want as your Default Printer in the Print & Fax system preference.)
5. Check for ink issues
If the printer's ink or toner is low, replace it. Low ink or toner is much more often a problem with inkjet printers than with laser printers. Making matters worse, many inkjet printers are notorious for not printing at all when even one of their multiple ink cartridges is empty. In other words, if your printer is out of yellow ink, you may not be able to print a black-and-white text-only document.
When your printer's ink needs to be replaced, you should get an alert message on both your Mac and the printer's display. If you don't see a warning but suspect a problem, select your printer in the Print & Fax system preference, click on Options & Supplies, and then click on the Supply Levels tab for information.
You might see only an "Information Not Available" message. In that case, use Spotlight (command-spacebar) to see whether your printer came with its own utility. (For example, I searched for Canon on my Mac and found the Canon IJ Printer Utility located in my /Library/Printers/Canon/BJPrinter/Utilities folder.) Try launching the utility directly. Note that printer utilities typically don't work if a printer is connected to a Mac over a network--for example, through an AirPort Base Station. To work around this, temporarily connect your printer directly to one of your Mac's USB ports.
Tip: A message that says you're low on ink may be incorrect. Especially if you haven't used the printer for a while, the problem may be that the print head's nozzles are clogged. To check for this, and hopefully fix the problem, clean the nozzles with the appropriate feature in the printer's utility. (The manual that came with your printer should provide details.)
When he isn't Twittering (@tedlandau), Macworld Senior Contributor Ted Landau is busy working on the third edition of Take Control of Your iPhone.